Method for folding an airbag

ABSTRACT

A method and device for folding an airbag having a inner main fold and an outer main fold in a folded state. The airbag is fixed to a working surface, extended along a longitudinal axis away from the working surface, and fixed in the area of the inner or outer main fold. The airbag is then expanded, or contracted, to form the outer or inner main fold, respectively, and then compressed toward the working surface. A shaping body is preferably inserted into the airbag through an inflation opening to extend the airbag so that a folding element may activated to retain the airbag against the shaping body to form the inner or outer main fold.

BACKGROUND OF THE INVENTION

The present invention relates generally to airbags, and moreparticularly to a method and apparatus for folding an airbag.

From German Patent No. DE 44 22 276 A1 an airbag is known for an airbagmodule where the collapsed airbag has main folds which run at least inpart along closed paths around an imaginary center on the substantiallyempty spread-out airbag. The closed main folds preferably describecircular paths or ellipses of slight eccentricity. Secondary folds arealso provided which arise naturally during collapsing of the airbag.

This path of the main folds has the advantage that the folded airbag canopen very quickly and easily. Particularly during the unfolding of suchan airbag there is not the danger that the inner pressure produced inpartial areas of the airbag will impede the opening of further folds.This airbag can thereby be used for driver, passenger and side airbags.The drawback with this folding is that the expense for folding isconsiderable particularly if the folding is carried out mechanically.

Furthermore from U.S. Pat. No. 4,173,356 an airbag is known which isfolded concertina-like in the direction of the blow-in mouth. The mainfolds thereby run along parallel straight lines. An airbag thus foldedcan unfold quickly and simply wherein it is only suitable for passengeror side airbags in this type of folding owing to its elongated shapewhich is essential for a sufficient volume. It could only be used as adriver airbag if the ends are turned in. There is then however thedanger that the inner pressure impedes the opening of some folds.

From U.S. Pat. No. 3,876,272 an airbag is known which has several innerand outer main folds relative to a longitudinal axis. An airbag foldedin this way can also unfold rapidly and quickly.

The objective of the invention is therefore to reduce the expense forfolding in the case of a universal airbag which is folded so that theinner pressure does not impede the opening of the folds.

SUMMARY OF THE INVENTION

With a method for folding an airbag which has in the folded state atleast one inner and one outer main fold wherein the latter runs at agreater distance from the longitudinal axis than the inner main fold,according to the invention the clamped airbag is pre-shaped so that itextends in the direction of a longitudinal axis on the sleeve face ofthe inner main fold or main folds provided. The airbag is then fixed inthe area of the inner main fold or inner main folds provided and ispressed or drawn outwards in the area of the outer main fold or mainfolds provided. The airbag is then compressed in the direction of itsclamping point.

With this method first the position of the sleeve face of the inner mainfold or main folds is fixed. The outer folds are then formed by slidingor drawing to the outside the parts of the airbag not fixed there. Theadvantage is that the folding process can be readily mechanized andautomated whereby the technical expense is reduced compared to knownfolding. Rapid folding is possible. This type of folding allows also afavorable storage of the gas generator which can also be insertedafterwards.

An alternative to the aforesaid method exists where the clamped airbagis pre-formed so that it extends in the direction of a longitudinal axison the sleeve face of the outer main fold or main folds provided, thatthe airbag is then fixed in the area of the outer main fold or foldsprovided and pressed or drawn inwards in the area of the inner main foldor main folds and that the airbag is then compressed in the direction ofits clamping point.

With this method thus first the position of the sleeve face of the outermain fold or main folds is fixed. The inner main fold or inner mainfolds are then formed by sliding or drawing inwards the parts of theairbag not fixed there.

In order to carry out the folding method the airbag is preferablyclamped in the area of its blow-in mouth or inflation opening whereinthe longitudinal axis about which the folding is carried out then runsapproximately perpendicularly through the blow-in mouth.

The shaping and temporary fixing of the airbag in the area of the outermain fold or main folds provided is preferably carried out by means ofcompressed air and the shaping and fixing of the airbag in the area ofthe proposed inner main fold or main folds is preferably carried out bymeans of mechanical aids.

In a preferred embodiment the method is designed so that the airbagprefitted on a generator support plate is tensioned over one or morehollow cylinders until it adjoins same and is completely stretched.Folding elements are then fitted on the airbag in the area of the innermain fold or main folds provided. These folding elements fix the airbagat the points where the inner main fold or the inner main folds areprovided. The hollow cylinder is then biased with compressed air whereinthe airbag is pressed outwards at the non-fixed points. The outer mainfolds are then formed in these sections which have been pressed to theoutside. These steps mentioned up until now substantially determine thesleeve faces in which lie the inner and outer main folds.

At the end of these aforementioned steps the hollow cylinder is thenpushed with the folding elements in the direction of the generatorsupport plate whereby the compressed air can escape. In this method stepthe final folding of the airbag takes place. At the end of the foldingprocess the folding elements and the hollow cylinder are removed andthen a cover cap and generator are fitted.

A device for carrying out the method is characterized in that a shapingbody is provided for pre-forming the airbag and that displaceablefolding elements are provided in a ring around these shaping bodies at adistance from the inner main fold or main folds provided across thelongitudinal axis of the shaping body.

In a preferred embodiment a hollow body is provided which has throughopenings on its sleeve face and can be attached to a compressed airsource. Compressed air is blown in through the openings into the airbagand this is then inflated in the areas of the outer main fold or mainfolds provided.

In a preferred embodiment a hollow cylinder is provided as a hollowbody.

A further embodiment proposes that the shaping body is mounted in anunderpressure or vacuum chamber. In this case the areas of the airbag inwhich the outer main fold or main folds are provided are then drawnoutwards.

In a further embodiment a shaping body is provided which has on itssleeve face or outer surface grooves for blowing in compressed air orsucking out air. In this embodiment the shaping body need not be ahollow body for supplying compressed air into the airbag.

Folding plates are preferably provided as folding elements and have aforked section which matches the path of the sleeve face of the hollowbody.

If several inner and outer main folds are provided the parts of the forklie in one plane.

If only one inner and one outer main fold are provided the forkedsection of the folding plate has mutually restricted parts. Theserestricted parts form with an off-set arrangement of the folding platesa spiral shaped line which corresponds to the inner main folding line .

Cables or tongs can also be used as folding elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in an embodiment with reference tothe drawings in which:

FIG. 1 is a sectional perspective view of a folded airbag;

FIG. 2 is a plan view of the expanded airbag with the main foldsprovided;

FIGS. 3-8 show the development of the folding process;

FIG. 9 is a plan view of the folding plates;

FIG. 10 shows the folding plates according to FIG. 9 in their workposition;

FIG. 11 is a longitudinal sectional view through a body for pre-formingthe airbag;

FIG. 12 is a cross-section through a shaping body with grooves forpre-forming the airbag;

FIGS. 13 a-c show airbags folded in different shape;

FIGS. 14 a,b show a conical shaping body and the folding of the airbagwhich can be achieved therewith;

FIGS. 15 a-c show a stepped hollow body as shaping body and the folds ofthe airbag which can be achieved thereby;

FIG. 16 shows an airbag packet with circumferential main folds in a sideview;

FIG. 17 shows the airbag according to FIG. 18 in plan view on theexpanded top plate;

FIGS. 18 a,b show a device for folding according to FIG. 18 by means ofcircumferential loops; AND

FIGS. 19 a-c show a device for folding according to FIG. 18 by means offolding plates.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of an airbag folded according to theinvention which is folded in the direction of a longitudinal axis A.With this type of folding outer main folds 2 and inner main folds 3 areprovided which follow each other alternately. The folds lie at a spacings from each other. FIG. 2 shows the spread-out airbag with the outer andinner main folds 2 and 3 provided therein. It can be seen that the mainfolds provided on the spread out airbag lie on closed paths of differentdiameter. Since the outer and inner main folds at the end of folding lieon paths with substantially the same diameter, during folding of theairbag secondary folds 4 are also formed in addition to the main foldsdeliberately provided and these secondary folds are formed naturally andarbitrarily, but in practice run approximately at right angles to themain folds. These secondary folds 4 are formed during folding of theairbag most markedly at the point where in order to achieve the uniformdiameter of the paths on which the main folds lie, the most material hasto be gathered in. As shown in FIG. 2 the secondary folds extend in thisarea from the outer main folds to the inner main folds.

As shown in FIGS. 3 to 8 the folding process takes place in theillustrated embodiment so that the airbag is prefitted on a generalsupport plate or working surface 6 in the area of its blow-in mouth orinflation opening 5. Then a shaping body or hollow cylinder 7 isinserted through this mouth 5 into the airbag 1. This hollow cylinderhas roughly the diameter of the gas generator as well as on itscircumference numerous through openings 8 which lie in particular inplanes of the outer main folds provided. The hollow cylinder is insertedso far into the airbag until the latter is completely stretched. Theairbag then adjoins the hollow cylinder. As a result of the roundgeometry of the airbag 1 illustrated in FIG. 2 longitudinal folds 9 areformed (FIG. 9).

In a next step a pressure plate 10 is placed against the airbag in thearea of the end face of the hollow cylinder. Furthermore folding plates11, 12 are placed against the airbag 1 in the planes of the inner mainfolds 3 provided. The folding plates 11, 12 have the forked shape shownin FIG. 9 and such a spacing in the vertical direction that as shown inFIG. 10 they can be pushed one over the other and engage on all sidesround the airbag tensioned around the hollow cylinder 7.

The hollow cylinder is then biased with compressed air. This enters theairbag 1 from the through openings 8 in its outer surface and pressesthe bag away from the outer surface hollow cylinder in the area of theouter main folds provided, as can be seen in FIG. 6. The hollow cylinder7 is then pushed together with the folding plates 11, 12 and pressureplate 10 towards the generator support plate 6. The folding of theairbag 1 is thereby carried out whereby the site of the main folds isfixed through the position of the folding plates 11, 12 and through thecompressed air. During folding the compressed air is let out of theairbag until the folding process is possible.

After folding has been completed as shown in FIG. 7, the folding plates11, 12 , pressure plate 10 and hollow cylinder 7 are removed. A covercap 13 and gas generator 14 can then be fitted.

The hollow cylinder shown in FIG. 11 has on its circumference in thearea of the folding plates 11, 12 circumferential notches 15 into whichcan engage the folding plates. During insertion of compressed air intothe airbag improved fixing of the airbag is thereby reached in the areaof the folding plates.

FIG. 12 shows a shaping cylinder 16 which can be used instead of theshaping cylinder 7. This shaping cylinder which can be formed equally asa hollow body or solid body, has grooves 17 spread out over itscircumference for supplying compressed air and running in the directionof the longitudinal axis of the shaping cylinder.

FIGS. 13 a to 13 c show folds of different size which can be achieved bymeans of folding plates of the type previously described but not shownand which are arranged at different intervals around a cylindricalshaping body. The spaces between the folding plates determine the sizeof the folds. In order to reach the path of the outer main folds 2according to FIG. 13 a the folding plates must have a smaller spacingstarting from the lower area of the shaping body upwards. For thefolding according to FIG. 13 b the distance between the folding platesis greatest in the middle of the shaping body and decreases from top tobottom. With the folding according to FIG. 13 c the distance between thefolding plates increases from bottom to top.

In FIG. 14 a a conical shaping body 18 is shown with an airbag 1 whichis to be folded, as well as the folding plates 11,12. The folding platesare arranged from bottom to top in an increasingly larger spacing sothat the airbag is formed in the manner shown in FIG. 14 b where thefolds become greater from bottom to top. Whilst the inner main folds 3lie on an imaginary conical sleeve the outer main folds 2 run on animaginary cylinder sleeve.

With the embodiment of FIG. 15 a a stepped hollow cylinder 19 isprovided as the shaping body. The airbag 1 which is to be folded ismounted over this and is enclosed by folding plates 11,12 in the mannerpreviously described. For a folding of the airbag as shown in FIG. 15 bwhere the path of the outer main folds 4 lies on a cylinder sleeve, alarger distance between the folding plates is required in the upper areawith smaller diameter of the inner main folds 3. For a folding of theairbag shown in FIG. 15 c by means of the stepped hollow cylinder 19where the outer main folds 4 have a smaller diameter in the area of thesmaller cylinder diameter of the shaping body the distance between thefolding plates is equal size.

In the embodiment of FIGS. 16 and 17 instead of several inner and outermain folds only one outer main fold 20 and one inner main fold 21 isprovided. These run spirally on an imaginary cylinder sleeve as shown inFIG. 16. From the illustrations in FIG. 17 with the plan view of thespread out airbag it is possible to see the main folds 20, 21 provided.It can be seen that the inner and outer main folds 20, 21 run into eachother at the ends.

From FIGS. 18 a and 18 b can be seen diagrammatically the structure of adevice for producing a folding according to FIG. 16. The empty airbag isfixed on the hollow cylinder 7 by means of a circumferential cable 22 atthe point of the inner main fold 21 provided. The airbag is then pushedaway from the hollow cylinder 7 by compressed air in the area of theouter main fold 20 provided and is compressed at the same time orafterwards.

The further processing steps correspond to that already described.

A further possibility for producing a folding with an inner and outermain fold line can be seen in FIGS. 19 a to c. The airbag 1 located onthe hollow cylinder 7 is associated with the folding plates 23 whoseforks have parts 24,25 restricted relative to each other. The forks ofthe folding plates are restricted so that a spiral circumferentialabutment of the airbag against the shaping body is produced (FIG. 19 b).The restricted forks must be movable so that the restriction decreasesduring compression of the airbag (FIG. 19 c).

What is claimed is:
 1. A method for folding an airbag such that when theairbag is in a folded state, the airbag has at least one inner main foldand at least one corresponding outer main fold, wherein the at least oneouter main fold is a greater distance from a longitudinal axis of theairbag than the at least one inner main fold, the method comprising thesteps of: clamping the airbag to a working surface; pre-shaping theairbag so that it extends along the longitudinal axis by inserting ashaping body into the airbag ugh an inflation opening, then fixing theairbag in the area of the at least one inner main fold; expanding theairbag to form the at least one outer main fold; and compressing theairbag in the direction of the clamping point.
 2. The method accordingto claim 1 wherein the airbag comprises an inflation opening, the airbagis tensioned around the inflation opening, and the longitudinal axisruns approximately perpendicular through the inflation opening.
 3. Themethod according to claim 2 wherein the expanding step comprises fillingthe airbag with compressed air and wherein the inner main fold is fixedby mechanical means.
 4. The method according to claim 3 wherein theshaping body comprises a hollow cylinder, wherein the shaping body isinserted into inflation body and the airbag is tensioned over the hollowcylinder until it adjoins the same and is completely stretched, whereinthe fixing step further comprises placing folding elements against theairbag to retain the airbag against the shaping body, wherein theexpanding step comprises biasing the hollow cylinder upward withcompressed air through the inflation opening, wherein the compressingstep comprises compressing the hollow cylinder with the folding elementstowards the working surface wherein the compressed air can escapethrough the inflation opening, and wherein the method further comprisesremoving the folding elements and hollow cylinder from the airbag andfitting the airbag with a cover cap and a generator.
 5. The methodaccording to claim 1 wherein the shaping body is cylindrical.
 6. Themethod according to claim 1 wherein the shaping body has an outersurface and wherein the fixing step comprises retaining the airbagagainst the outer surface of the shaping body.
 7. The method accordingto claim 6 wherein the expanding step comprises filling the airbag withair through the inflation opening.
 8. The method according to claim 7wherein the compressing step further comprises compressing the shapingbody toward the working surface while the airbag is retained against theouter surface of the shaping body to expel the air within the airbagthrough the inflation opening.
 9. The method according to claim 7wherein the shaping body comprises a hollow interior and a plurality ofopenings extending from the hollow interior to the outer surface of theshaping body, and wherein the filling step comprises filling theinterior of the shaping body with compressed air so that the air willflow through the plurality of openings and into the airbag.
 10. Themethod of claim 1 wherein the airbag in its shaped and extended form issubstantially radially arranged around the longitudinal axis.
 11. Themethod of claim 1 wherein the airbag is clamped, shaped, fixed, andexpanded in its unfolded configuration, such that the expansion stepfirst forms the at least one outer main fold and the compressing stepcompletes formation of the outer and inner main folds.
 12. The method ofclaim 1 wherein the at least one inner main fold and at least one outermain fold are formed from a single layer of the airbag.
 13. The methodof claim 1 wherein the shaping body is air.